Overload protective device



Jan. 2, 1951 H. N. SLACK OVERLOAD PROTECTIVE DEVICE Filed Sept. 14, 1946 Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE OVERLOAD PROTECTIVE DEVICE Howard N. Slack, Los Angeles, Calif.

Application September 14, 1946, Serial No. 697,035

4 Claims.

My invention in its broadest aspect pertains to a torque responsive overload protection device. I have developed this invention in connection with, and have applied it to, a frozen food mixer adaptable to domestic mechanical refrigeration cabinets. Whereas, the specifications hereinafter to follow will describe my invention in connection with an ice cream freezer adapted to domestic refrigeration cabinets, it will be understood that the overload protection device above referred to may be applicable to a wide variety of uses wherein it is desired to protect any power mechanism against a torque overload.

In the manufacture of ice cream, it is essential to continuously agitate the mixture while it is being congealed in order to prevent either the separation of any of the constituent materials or the formation and growth of ice crystals. This purpose is accomplished by the rotating of a plurality of paddles in the container into which the constituent mixture has been placed for freezing. The rotation of the paddles may be accomplished by, among others, the use of an electric motor. The principal weakness of such a system lies in the fact that as the constituent mixture begins to congeal, its viscosity becomes greater thereby increasing the torque loading of the electric motor. This will reach a point where it is dangerous to the safety of the electric motor.

It is an object of my invention to provide a device for coupling the drive shaft of the electric motor to the shaft of the paddle assembly, which will be responsive to a torque loading and disconnect the electric circuit when the torque load reaches a predetermined maximum.

Numerous overload protection devices are known to the art. Most of the heretofore known overload protection devices are complicated in their structure and expensive to manufacture. It is a further object of my invention to provide such a torque responsive overload protection which will be simple and inexpensive to manufacture and easily assembled into the domestic refrigeration cabinet.

A further specific object of my invention is to provide a container for freezing various types of food, such as ice cream, which is not permanently attached to the refrigeration cabinet thereby economizing in the use of space within the cabinet, and which is, at the same time, easily operable and easy to assemble and remove. Further objects and advantages of my invention will become apparent from the drawings and specifications relative thereto.

In the drawings:

Figure 1 is a side elevation, partially in section, of an ice cream freezer embodying the principles of my invention.

Figure 2 is an end elevation taken from the right-hand side of Figure 1.

Figure 3 is a partial plan view of the righthand end of Figure 1.

Figure i is a sectional view taken on line 44 of Figure 1.

Figure 5 is a detailed plan view, partially in section, of the torque responsive protective device.

Figure 6 is a detailed section view of the mounting or the drive shaft through the cabinet Wall.

Figure 7 is an enlarged detailed view of the coupling device between the drive shaft and the ice cream freezer.

The essential features of my invention in the preferred embodiment include a freezing container it disposed within an evaporator coil ii, an electric motor [2, and a torque responsive overload protection designated generally i3, mounted in an undercut portion of a refrigerator cabinet M.

The freezing container In is generally of a standard construction and comprises a cylindrical container 20 closed at one end by a bottom 2| as an integral part thereof, and closed at the other end by a removable cover 22. The removable cover 22 is formed with 9. depending annular flange 23 adapted to frictionally engage the cylindri al wall 26. Sealing means are provided; such as the rubber gasket 24 to render the joint between the cover 22 and the cylindrical wall 20 liquid tight. The cover 22 is formed also with an axially disposed boss 25 having a bore 26 disposed therethrough into which a bearing surface 2? is secured by any suitable means, such as a friction fit. The bottom 21 is formed with a centrally disposed boss 23 having a centrally disposed bore 2-) therein.

Any suitable means may be provided for agitating the constituent mixture as it is being congealed. I prefer and have illustrated an agitating device which comprises a plurality of paddles attached to a plurality of radially extending arms 35 and disposed adjacent and par allel to the cylindrical Wall 29. The radially extending arms 3! are securely attached to a centrally disposed pivot point 32 on one end, and a centrally disposed driving shaft 33 on the other end formed at its free end with any suitable nonrotatabl-e couple, such as the square end 33a. The pivot point 32 is adapted to pivot or rotate in the bore '29. The shaft 32 is rotatably disposed in the bore 26. Mean for driving or rotating the paddle assembly comprise any standard electric motor, such as motor I2. The motor I2 is mounted externally on the refrigeration cabinet M by means of bolts 34.

Means for coupling a drive shaft I2a or" motor I2 to the driven shaft 33 of the paddle assembly include the overload protective device 13. The overload "protective device I3 comprises "a cupshaped member having a centrally disposed boss 4I formed with a bore 62 therethrough, a driving member or radial arm 43 having a centrally disposed boss 44 formed witha centrally disposed bore 45 therethrough. It w'ill'be understood that a spider or any other suitable bracket will be considered as an equivalent of the cupshaped member 40. A plurality of axially directed pivot posts 45 are securely mounted-"in the cup 40 by any suitable means, such as for example, projection welding. Pivot posts d6 are formed Wit-11 51011841111 theupper end thereof. A plurality of-camming members is are 'pivotally disposed'in the slots 4?. The oup ltis formed with a-p-lurality of :inwardly extending loops 59. The camming member 53 15 urgedinto ngagement with the radial arm 43 bymeans of springs 5I or other suitable biasing'means connected in tension-between the :camming member 48 and the loops 58. The cup 45 is also formed with a plurality of slots 52 in the base of said cup adapted so that uponirotation of the camming memberiihthe end thereof will pass through the slot52. A plate 60 vispivotalh; mounted by being securedto pivot rod-.6 hand if formed with apro- Ijectionffiz extendingat r ightrangles to the principal plane of plate '60 and a centrally disposed elliptical bore 53. Theoplate fit'is pesitioned with respectlto the cup '49 sothat upon v otation the camming members Bathe camming members lwillpress against the plate 59 and cause it to rotate in a counter-clockwise direction taken in the viewof Figure 11.

"The'means for connecting the cup ie with the paddl -assembly comprise a shaft Hi disposedin "the'bore 32 of the boss 4i, and is detachably connected to the shaft 33 by means of a spline fitting which comprises members "II and E2. The spline member "1! is formed with slidable couple Ha adapted Tao-cooperate with the square-end 33a so that "it is slidably and non-rotatably mounted on the end l-of shaft 33 and'is urged outwardly from shaft "33 by means o'fa spring F3. The spline member 12 is securely mounted on'the shaft H? by any'suitable means, such as a pin or a lefthand thread.

The shaftlii is rotatably mounted through the wall of the cabinet it by means of an assembly which comprises a substantially tubular-shaped member '89, which is internally threaded at the inner end iii and externally'threaded at the outer end 82. .Alock nutlBS secures the outer end 82,

and afian'ge'dmember 85 secures the inner end of the "tubular member Bil in the wall H! of the .cabinet. The flanged'member 84 is 'formed'with a centrallydisposedbore 85 adapted to receive a spring 33, which urges a sealing ring 87 against a washer '33 and a smaller bore 89 adapted'to receive a bearing 90. The shaft is is formed with a shoulder st to prevent the shaft Hi from being urged through the bore 88 by the spring 85.

'Th'e'freezing container is removably and nonrotatably mounted in the evaporator coil H by meansof the bracket lei} which is secured to the "base "2| of the container is and is prevented from rotatingby means-of lugs NH. The bracket IDS is formed in a substantially U-shape, having substantially S-shaped arms I92 adapted to engage the sides of the evaporator unit Ii.

When it is desired to insert the freezing unit it into the evaporator coil H and into operative connection with the drive shaft '59, the unit is pushed into the evaporator coil with the spline member ii approximately aligned with the spline member 52. In the event that'the splines do not match, the freezing unit it may be pushed inwardly of the coil l I until the bracket IUD se- 'curely engages the sides of the evaporator coil II. The spline member 7! will be urged inwardly on shaft 33. As soon as the motor I2 commences to drive theshaft ill and rotate the spline member I2, the splines of the spline members ll and I2 willbec'ome matched, and the spline member I2 will be urged outward1y on shaft 33 by means of the spring 13.

Uponremoval of the freezing :unit-Ilt-from the evaporator coil ii, the splin member i2 may =be covered by a cap it adapted to fit over the flanged member S's-in frictional engagement.

The operation of my overload protective device is as follows: The motor if bein operatively connected to the radialarm 53 rotates the arm-43 in a counter-cleckwise direction (Figure i). "The ramming members 48 are urged against the l ading edge of the radialarms E3 by means of the springs 5!, thereby causing the cup i iialsoto rat-ate ina counter-clockwise direction.

When the constituent mixture in the freezing container 1 congeals to a predetennined viscosity the torque required to rotate the paddles '30 becomes greater than the strength of the springs 5!. The springs-5| therefore yield and the camming members at are caused to rotate outwardly fromthe center of the cup '49 until they engage the surface of theplatetc. The plate 'Eili is then caused to rotate in a counter-clockwise direction (Figure l) thereby raising the projecting'arm 52 into contact with the normally closed 'microswitch 5 2. When the projecting arm 62 has been displaced at predetermined distance, the microswitch 6 t opens, thereby "breaking the circuit which is energizing the'rhot'or I l, andturiiih'g'oif the assembly.

It will be obvious that the motor shaft 420, and the freezer coupling shaft iii are axially aligned, and that they constitute in effect a single shaft in two separated sections. in the claims the latter phrase is employed; namely, 'a shaft in two'sep rated but axially aligned sections,-as a'matter'of convenience, and is intended-to include the obvious equivalent of two individual axially aligned shafts.

While I have herein shown and described my invention in what I have conceived 'to be "the most practical and preferred embodiment, iti's recognized that departures may be"m'adetherefrom within the scope of my invention, "which is not to be limited to thedetails disclosedherein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent device's.

Having described my inventionfw hat I claim-as new and desire to secureby Letters Patentis:

1-. A torque coupling and protective device "for an electric motor comprising a shaftin two separated lout axially aligned sections, a .pair of diametrically opposed radial arm's secured "to one of said sections for rotation therewith, "a pair of camming members associated with "the other of said sections for rotation therewith and adapted to engage one edge of said radial arm, resilient means adapted to "bias said ramming members into contact with said arms but to yield to permit pivotal movement of said camming members upon the application of an excessive torque, a lever positioned adjacent said camming members for contact thereby upon application of an excessive torque through said torque coupling and adapted upon said torque application to actuate a switch for controllin said electric motor.

2. A torque coupling and protective device for an electric motor comprising a shaft in two separated but axially aligned sections, a radial arm Secured to one of said sections for rotation therewith, a camming member associated with the second of said sections for rotation therewith and adapted to engage one edge of said radial arm tov cause rotation of said other section, a sprin member associated with said second shaft section for rotation therewith and adapted to bias said camming member into contact with said arm but to yield to permit pivotal movement of said camming member upon the application of an excessive torque, a pivotal switch actuating plate positioned adjacent said camming member for contact therewith upon application of an excessive torque through said torque coupling and adapted upon said torque application to actuate a switch for controlling said electric motor.

3. In combination with an electric motor and a control switch therefor, a. torque transmitting and overload protective device comprising a shaft in two sections in axial alignment, a radial arm associated with one of said sections for rotation therewith, a cup associated with the other of said sections for rotation therewith, said cup having a base and side wall, a pair of camming fingers pivotally secured to said cup, each of said fingers having an edge adapted to abut against the leading edge of said radial arm, resilient means adapted to bias said fingers into abutment with said radial arm, and to yield upon the application of an excessive torque to cause a pivoting motion of said finger, a switch actuating plate pivotally mounted adjacent said cup so that said switch plate will be contacted and pivoted by a pivoting of said cam finger, said switch actuating plate being adapted to actuate said control switch upon being pivoted by said camming finger.

4. In combination with an electric motor and a control switch therefor, a torque transmitting and overload protective device comprising a shaft in two sections and axially aligned, and resilient means for coupling said sections together for torque transmission, said means comprising a radial arm associated with one of said sections for rotation therewith, a cup secured to the other of said sections for rotation therewith and adapted to enclose said radial arm, said cup having a base and side wall, a pair of camming fingers pivotally secured to said cup, each of said fingers having an edge adapted to abut against said radial arm, resilient means adapted to bias said fingers into abutment with said radial arm, and to yield upon the application of an excessive torque to cause a pivoting motion of said fingers, said means comprising a tension spring secured between each of said fingers and the wall of said cup on the opposite side of said arm, a switch actuating plate pivotally mounted adjacent said cup so that said switch plate will be contacted and pivoted by a pivoting of said cam fingers, said switch actuatin plate being adapted to actuate said control switch upon being pivoted by said camming fingers.

HOWARD N. SLACK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,996,849 Bauer Apr, 9, 1935 2,232,545 Lum Feb. 18, 1941 FOREIGN PATENTS Number Country Date 519,194 Great Britain Mar. 19, 1940 

